Monocyte culture and adherence modifies LPS-induced IL-6 production and inhibition by hydrocortisone

The effect of hydrocortisone (HC) on IL-6 production by monocytes (Mo) that were cultured under either adherent or limited-adherent culture conditions was determined. Although freshly isolated Mo produced more IL-6 in response to LPS than Mo cultured 24 hr, culture had little effect on inhibition of IL-6 by HC. In contrast, the conditions of Mo culture had a significant impact on the kinetics of IL-6 production and inhibition by HC. Adherent Mo produced significantly higher levels of IL-6 4 hr after LPS compared to limited-adherent Mo. By 12 hr of LPS stimulation, comparable quantities of IL-6 were produced by both cultures. HC inhibition was complete 4 hr after LPS stimulation of adherent Mo, while 12 hr was required for maximum inhibition of limited-adherent Mo. Production of an IL-6 inhibitor was not responsible for the increased inhibition by HC with adherence, because both IL-6 protein and bioactivity were comparably decreased. The kinetics of inhibition of TNF alpha and IL-1 beta production by HC were similarly affected by adherence. Phenotypic analysis of cultured vs freshly isolated Mo showed a decrease in Mo expressing CD14, but not CD11b, which paralleled a decrease in IL-6 production by the cultured Mo. However, there were no phenotypic differences between adherent and limited-adherent Mo. The results demonstrate that the time of Mo culture, as well as adherence, may serve to alter LPS-induced IL-6 production and its inhibition by HC.